EFFECTS OF EXPOSURE TO RADIOACTIVE 56MnO2 POWDER ON HYALURONAN SYNTHASE 2 IN THE LUNGS OF RATS.

Manganese-56 (56Mn) is among the predominant radioisotopes produced in soil by neutrons from atomic bombs. Previously, we examined the effects of the internal exposure of this radioisotope in Wistar rats and reported significant pathological changes in the lung and small intestine. In the present study, we focused on its effects on hyaluronan synthase 2 (Has2) gene expression that may related to pathological changes in the lung. Ten-week-old male Wistar rats were exposed to neutron-activated 56MnO2 powder, non-radioactive MnO2 powder or external 60Co γ-rays (2 Gy, whole body). Animals were examined on days 3, 14, and 60 post-exposure. Absorbed doses in the lung of rats exposed to 56Mn were 55-110 mGy. Quantitative reverse transcription polymerase chain reaction analysis revealed that 56Mn exposure significantly reduced the expression of Has2 gene in the lung, while γ-rays did not change it. Our findings suggest that internal exposure to 56Mn, even at low doses, has a significant biological impact on the lung compared with external radiation.

[RESEARCH OF INTESTINAL MICROFLORA IN THE RATS FOLLOWING THE INTERNAL AND EXTERNAL IRRADIATION].

The aim of the research was comparative investigation of the quantitative and qualitative composition of large intestinal microflora following internal (by dispersed powdered 56Mn) and internal exposure of Wistar rats. Ten weeks-old male Wistar rats were used. Rats were divided into four groups: L-56Mn group with 12 rats, H-56Mn with ten rats, 60Co group with nine rats and control group with nine rats. L-56Mn and H-56Mn groups were exposed to two different doses of 56MnO2 powder. 60Co group received 2 Gy of external 60Co γ-ray whole body irradiation. Totally 40 rats. Three rats from each group were sacrificed throw 6 hours and on days 3, 14, and 60 after the exposure. Animals were examined throw 6 hours and on days 3, 14 and 60 after exposure. Although the absorbed doses in large intestine were only 0.69 and 1.90 Gy in 56Mn exposed groups, respectively, changes in large intestinal microflora were evident. After 6 hours and on day 3 after 56Mn exposure amount of main representatives of large intestinal microflora (Bifidobacterium and lactobacilli) was decreased in the dose dependent manner. On the other hand, the amount of conditionally pathogenic bacteria was increased. These changes were persistent even on day 14. External 60Co γ-irradiation at a dose of 2 Gy also changed the intestinal microflora, but these changes were not persistent and on day 14 after irradiation returned to the control level. Our data suggest that internal exposure to dispersed powdered 56Mn has a significant biological impact on the intestinal microflora for a prolonged period of time, when it is compared with the effects of external radiation.

[INFLUENCE OF IONIZING RADIATION ON THE LOCOMOTOR ACTIVITY AND BODY WEIGHT OF RATS].

The aim of our study was to study influence of ionizing radiation on the locomotor activity and body weight of rats, for this animals was irradiated by via inhalation. Beta- emitter 56Mn was obtained by neutron activation of powdered MnО2 by using nuclear reactor IVG.1M (experimental facility «Baikal-1¼, Kurchatov, Kazakhstan). Exposure of rats to radioactive powder had two way, the first experiment was contained only air filter for animal's breathing and the second with the system of forced ventilation. Also we developed the method for observation of the locomotor activity of rats, based on quantitative data. The experiment was conducted on 8 «Wistar¼ breed white laboratory rats. Statistical analysis was performed using descriptive statistics and non-parametric test. Based on our data, we can say that our method has the advantage over the others is that there is no need to move about the animal out of the box in the test field. So we reduce animal stress factor, as the transfer of an animal from one to second place creates additional stress for him. The initial activity of the pulverized powder in both experiments were 2,74х108Bq, but in the second experiment when we used the system of forced ventilation, internal radiation doses were 0.041±0.0075 Gy, this didn't have effect on locomotor activity of rats (Z= -0,841, р=0,4). In the first experiment where we used only air filter for animal's breathing internal radiation doses were 0.15±0.025 Gr, that showed a decrease in locomotor activity in rats (Z=-6,653, р=0,001). After exposure to ionizing radiation changes in the mammals' weight were not found. Thus, based on our data we have made conclusion, that even after a single irradiation at low dose 0.15±0.025 Gr changes occur in the nervous system.